Synthesis of core-shell polymer particles in supercritical carbon dioxide iterative monomer addition.

A new, robust methodology for the synthesis of polystyrene-poly(methyl methacrylate) (PS-PMMA) core-shell particles using seeded dispersion polymerisation in supercritical carbon dioxide is reported, where the core-shell ratio can be controlled predictably manipulation of reagent stoichiometry. The key development is the application of an iterative addition of the MMA shell monomer to the pre-prepared PS core. Analysis of the materials with differing core-shell ratios indicates that all are isolated as single particle populations with distinct and controllable core-shell morphologies.

Tailoring Pyro-and Orthophosphate Species to Enhance Stem Cell Adhesion to Phosphate Glasses.

Phosphate-based glasses (PBGs) offer significant therapeutic potential due to their bioactivity, controllable compositions, and degradation rates. Several PBGs have already demonstrated their ability to support direct cell growth and in vivo cytocompatibility for bone repair applications. This study investigated development of PBG formulations with pyro- and orthophosphate species within the glass system (40 - x)PO·(16 + x)CaO·20NaO·24MgO (x = 0, 5, 10 mol%) and their effect on stem cell adhesion properties.

Halide Mixing and Phase Segregation in CsAgBiX (X = Cl, Br, and I) Double Perovskites from Cesium-133 Solid-State NMR and Optical Spectroscopy.

All-inorganic double perovskites (elpasolites) are a promising potential alternatives to lead halide perovskites in optoelectronic applications. Although halide mixing is a well-established strategy for band gap tuning, little is known about halide mixing and phase segregation phenomena in double perovskites. Here, we synthesize a wide range of single- and mixed-halide CsAgBiX (X = Cl, Br, and I) double perovskites using mechanosynthesis and probe their atomic-level microstructure using Cs solid-state MAS NMR.

Low dimensional nanostructures of fast ion conducting lithium nitride.

As the only stable binary compound formed between an alkali metal and nitrogen, lithium nitride possesses remarkable properties and is a model material for energy applications involving the transport of lithium ions. Following a materials design principle drawn from broad structural analogies to hexagonal graphene and boron nitride, we demonstrate that such low dimensional structures can also be formed from an s-block element and nitrogen. Both one- and two-dimensional nanostructures of lithium nitride, LiN, can be grown despite the absence of an equivalent van der Waals gap.

Catalytic nanosponges of acidic aluminosilicates for plastic degradation and CO to fuel conversion.

The synthesis of solid acids with strong zeolite-like acidity and textural properties like amorphous aluminosilicates (ASAs) is still a challenge. In this work, we report the synthesis of amorphous "acidic aluminosilicates (AAS)", which possesses Brønsted acidic sites like in zeolites and textural properties like ASAs. AAS catalyzes different reactions (styrene oxide ring-opening, vesidryl synthesis, Friedel-Crafts alkylation, jasminaldehyde synthesis, m-xylene isomerization, and cumene cracking) with better performance than state-of-the-art zeolites and amorphous aluminosilicates.

The effect of MgO/TiO on structural and crystallization behavior of near invert phosphate-based glasses.

Varying formulations in the glass system of 40P O ─(24 - x)MgO─(16 + x)CaO─(20 - y)Na O─yTiO (where 0 ≤ x ≤ 22 and y = 0 or 1) were prepared via melt-quenching. The structure of the glasses was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), micro Raman and solid-state nuclear magnetic resonance (NMR) spectroscopies. The thermal properties and the activation energy of crystallization (E ) were measured using thermal analysis and the Kissinger equation, respectively.

Ion exchange and binding in selenium remediation materials using DNP-enhanced solid-state NMR spectroscopy.

Selenate-loaded selenium water remediation materials based on polymer fibres have been investigated by dynamic nuclear polarization (DNP) enhanced solid-state NMR. For carbon-13 a significant reduction in experiment time is obtained with DNP even when compared with conventional carbon-13 NMR spectra recorded using larger samples. For the selenium remediation materials studied here this reduction allows efficient acquisition of {H}-Se heteronuclear correlation spectra which give information about the nature of the binding of the remediated selenate ions with the grafted side chains which provide the required ion exchange functionality.

Mammalian-Cell-Driven Polymerisation of Pyrrole.

A model cancer cell line was used to initiate polymerisation of pyrrole to form the conducting material polypyrrole. The polymerisation was shown to occur through the action of cytosolic exudates rather than that of the membrane redox sites that normally control the oxidation state of iron as ferricyanide or ferrocyanide. The data demonstrate for the first time that mammalian cells can be used to initiate synthesis of conducting polymers and suggest a possible route to detection of cell damage and/or transcellular processes through in situ and amplifiable signal generation.

Gallium incorporation into phosphate based glasses: Bulk and thin film properties.

The osteogenic ions Ca, P, Mg, and antimicrobial ion Ga were homogenously dispersed into a 1.45 µm thick phosphate glass coating by plasma assisted sputtering onto commercially pure grade titanium. The objective was to deliver therapeutic ions in orthopaedic/dental implants such as cementeless endoprostheses or dental screws.

Structure of Ancient Glass by Si Magic Angle Spinning NMR Spectroscopy.

Si magic angle spinning (MAS) NMR spectroscopy has been applied for the first time to the structural analysis of ancient glass samples obtained from archaeological excavations. The results show that it is possible to establish the distribution of Si environments in ancient glass by Si MAS NMR, so long as the concentrations of magnetic impurities, such as Mn and Fe oxides, are low. In general, good agreement has been obtained with compositions determined by means of electron probe microanalysis.

H CSA parameters by ultrafast MAS NMR: Measurement and applications to structure refinement.

A H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν and ultrafast MAS to resolve H sites in ν is described. This experiment is used to measure H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes.

Measuring (19)F shift anisotropies and (1)H-(19)F dipolar interactions with ultrafast MAS NMR.

A new (19)F anisotropic-isotropic shift correlation experiment is described that operates with ultrafast MAS, resulting in good resolution of isotropic (19)F shifts in the detection dimension. The new experiment makes use of a recoupling sequence designed using symmetry principles that reintroduces the (19)F chemical shift anisotropy in the indirect dimension. The situations in which the new experiment is appropriate are discussed, and the (19)F shift anisotropy parameters in poly(difluoroethylene) (PVDF) are measured.

The role of copper(II) in the aggregation of human amylin.

Amylin is a 37-residue peptide hormone produced by the islet β-cells of pancreas and the formation of amylin aggregates is strongly associated with β-cell degeneration in type 2 diabetes, as demonstrated by more than 95% of patients exhibiting amylin amyloid upon autopsy. It is widely recognized that metal ions such as copper(II) have been implicated in the aggregation process of amyloidogenic peptides such as Aβ and α-synuclein and there is evidence that amylin self-assembly is also largely affected by copper(II). For this reason, in this work, the role of copper(II) in the aggregation of amylin has been investigated by several different experimental approaches.

Measuring proton shift tensors with ultrafast MAS NMR.

A new proton anisotropic-isotropic shift correlation experiment is described which operates with ultrafast MAS, resulting in good resolution of isotropic proton shifts in the detection dimension. The new experiment makes use of a recoupling sequence designed using symmetry principles which reintroduces the proton chemical shift anisotropy in the indirect dimension. The experiment has been used to measure the proton shift tensor parameters for the OH hydrogen-bonded protons in tyrosine·HCl and citric acid at Larmor frequencies of up to 850 MHz.

Insight into lithium transport in lithium nitridometallate battery materials from muon spin relaxation.

Muon spin relaxation and powder neutron diffraction have been combined to study three lithium cobalt nitride battery materials. Neutron diffraction shows that these retain the P6/mmm space group of Li(3)N with Co located only on Li(1) sites. The lattice parameters vary smoothly with the degree of metal substitution, such that the [Li(2)N] layers expand while the layer separation contracts, as observed previously for similar series of Cu- and Ni-substituted materials.

Pore with gate: enhancement of the isosteric heat of adsorption of dihydrogen via postsynthetic cation exchange in metal-organic frameworks.

Three isostructural anionic frameworks {[(Hdma)(H(3)O)][In(2)(L(1))(2)]·4DMF·5H(2)O}(∞) (NOTT-206-solv), {[H(2)ppz][In(2)(L(2))(2)]·3.5DMF·5H(2)O}(∞) (NOTT-200-solv), and {[H(2)ppz][In(2)(L(3))(2)]·4DMF·5.5H(2)O}(∞) (NOTT-208-solv) (dma = dimethylamine; ppz = piperazine) each featuring organic countercations that selectively block the channels and act as pore gates have been prepared.

Structure, stoichiometry and transport properties of lithium copper nitride battery materials: combined NMR and powder neutron diffraction studies.

A combined NMR and neutron diffraction study has been carried out on three Li(3-x-y)Cu(x)N materials with x=0.17, x=0.29 and x=0.

Solid-state nuclear magnetic resonance studies of vinyl polymer/silica colloidal nanocomposite particles.

Solid-state nuclear magnetic resonance (NMR) has been used to characterize the interface between the organic and inorganic components of "core-shell" colloidal nanocomposite particles synthesized by in situ aqueous (co)polymerization of styrene and/or n-butyl acrylate in the presence of a glycerol-functionalized silica sol. Polymer protons are in close proximity (<5 A) to surface silanol sites in all the nanocomposites studied, indicating that either styrene or n-butyl side groups extend between the glycerol-functional silane molecules toward the surface of the silica particles. For the poly(styrene-co-n-butyl acrylate)/silica nanocomposite n-butyl acrylate residues are located closer to the surface of the silica particle than styrene residues, suggesting a specific interaction between the former and the glycerol-functionalized silica surface.

Measurements of relative chemical shift tensor orientations in solid-state NMR: new slow magic angle spinning dipolar recoupling experiments.

Solid-state NMR experiments can be used to determine conformational parameters, such as interatomic distances and torsion angles. The latter can be obtained from measurements of the relative orientation of two chemical shift tensors, if the orientation of these with respect to the surrounding bonds is known. In this paper, a new rotor-synchronized magic angle spinning (MAS) dipolar correlation experiment is described which can be used in this way.

Sensitive absorptive refocused scalar correlation NMR spectroscopy in solids.

A new two-dimensional NMR experiment is described which is suitable for obtaining magic angle spinning (MAS) scalar correlation spectra in solids. The new experiment has several advantages, including increased cross peak intensities, coupled with good suppression of the diagonal. Its utility is demonstrated via assignments of the carbon-13 MAS spectra of progesterone at natural abundance and of the polymer phase of 50%-U-13C-CsC60.

Carbon-13 chemical shift tensors of disaccharides: measurement, computation and assignment.

A recently developed chemical shift anisotropy amplification solid-state nuclear magnetic resonance (NMR) experiment is applied to the measurement of the chemical shift tensors in three disaccharides: sucrose, maltose, and trehalose. The measured tensor principal values are compared with those calculated from first principles using density functional theory within the planewave-pseudopotential approach. In addition, a method of assigning poorly dispersed NMR spectra, based on comparing experimental and calculated shift anisotropies as well as isotropic shifts, is demonstrated.

Crystal chemistry and electronic structure of the metallic lithium ion conductor, LiNiN.

The layered ternary nitride LiNiN shows an interesting combination of fast Li+ ion diffusion and metallic behavior, properties which suggest potential applications as an electrode material in lithium ion batteries. A detailed investigation of the structure and properties of LiNiN using powder neutron diffraction, ab initio calculations, SQUID magnetometry, and solid-state NMR is described. Variable-temperature neutron diffraction demonstrates that LiNiN forms a variant of the parent Li3N structure in which Li+ ion vacancies are ordered within the [LiN] planes and with Ni exclusively occupying interlayer positions (at 280 K: hexagonal space group Pm2, a = 3.

CAESURA: measurement of slow molecular dynamics by solid-state nuclear magnetic resonance chemical shift anisotropy modulation amplification.

An alternative magic angle spinning (MAS) exchange NMR experiment based on chemical shift anisotropy (CSA) amplification is described. The CSA amplification experiment correlates a standard MAS spectrum in the omega(2) dimension with a sideband pattern in omega(1) in which the intensities are identical to those expected for a sample spinning at some fraction 1N of the actual rate omega(r). In common with 2D-PASS, the isotropic shift appears only in the omega(2) dimension, and long acquisition times can be avoided without loss of resolution of different chemical sites.

Theoretical study of the 13C NMR spectroscopy of single-walled carbon nanotubes.

The 13C NMR spectroscopy of armchair and zigzag single-walled carbon nanotubes has been investigated theoretically. Spectra for (4,4), (5,5), (6,6), (6,0), (9,0), and (10,0) nanotubes have been simulated based on ab initio calculations of model systems. The calculations predict a dominant band arising from the carbon atoms in the "tube" with smaller peaks at higher chemical shifts arising from the carbon atoms of the caps.

Chemical shift anisotropy amplification with high amplification factor and improved sensitivity.

An improved version of the recently proposed chemical shift anisotropy amplification experiment is described. The original experiment correlates a fast magic angle spinning spectrum in the omega2 dimension with a sideband pattern in omega1 in which the intensities mimic those for a sample spinning at a fraction of the rate omegar/N. Advantages of the experiment include the use of standard methods to extract the principal tensor components from the omega1 sideband patterns and the small number of t1 increments required.